Enterprise adoption of SDNs is lagging that of service providers due to several factors, primarily the criticality of the network itself.To service providers, the network is the business. To enterprises, the network enables or supports its core business.

That was abundantly clear at last week's OpenDaylight Summit, where all of the non-vendor and non-developer presenters were service providers. OpenDaylight is an open source SDN framework developed by 154 contributors, including major vendors, under the auspices of the Linux Foundation.

SDNs and Network Functions Virtualization (NFV), the method of virtualizing service provider network services, are considered key to enabling service providers to quickly create and provision new revenue generating services. The services are the lifeblood of the service provider's business.

Conversely, the lifeblood of the business of most enterprises is manufacturing a product or offering a service to sell. The network and its applications support the product or service creation, but is not the sellable product or service in and of itself.

Moreover, cloud computing is also driving SDN and NFV adoption in the service provider realm. Providers are employing the technologies to virtualize and elasticize their networks to support the cloud computing phenomenon, whereby they offer IT services to enterprises looking to offload their dedicated compute infrastructures.

Enterprises are also largely dependent on a single vendor for their network infrastructures: Cisco. With a dominant market share in enterprise switching and routing, Cisco is loath to disrupt that multibillion dollar installed base with advances like SDN. Similarly, enterprises have invested heavily in infrastructure and training, and grown accustomed to doing things the Cisco way for decades.Indeed, while most in the industry consider Cisco's Application Centric Infrastructure fabric to be the company's response to SDNs, Cisco asserts that the hardware-laden strategy is not SDN at all.

The numbers bear out the mismatch in SDN adoption between enterprises and service providers. Sales of software-defined networking products for live service provider deployments are estimated to reach $15.6 billion by 2018, while those that have live deployment potential will reach $29.5 billion, according to ACG Research.

Enterprise and cloud/service provider data center "in use" SDNs are a fraction of that: $3.1 billion by 2017, according to Infonetics Research.

"Service providers are turning over their data centers a lot faster and pushing the envelope," says Lee Doyle, principal analyst at Doyle Research. "Enterprises are a little more cautious and have slower refresh cycles."

"I think there are a smaller number of players that are more organized in the service provider world," says Cliff Grossner, directing analyst for data center and cloud at Infonetics. "They're much more highly focused on a select set of use cases. I don't think they have the same focused environment in the enterprise side."

But the service provider SDN/NFV universe is much larger than the enterprise. In sizing the market, ACG found that cloud and application data centers will be the busiest of four service provider domains -- data center, IP edge, metro and core -- until 2016, representing over 50% of SDN sales into live deployments. By the end of the forecast period, edge and metro areas will each become larger than the data center domain, with the uptake of SDN in advanced transport and IP services ramping along with deployments in the cloud.

Similarly, Infonetics last found that the top five network domains targeted by operators for SDN and NFV are: within data centers; between data centers; operations and management; CDNs; and cloud services. Eighty-six percent of surveyed operators also plan to deploy SDN and NFV technology in their optical transport networks as well, once standards are finalized, according to Infonetics.Driving all of this will be virtualization and consumer appetite for media and entertainment, social networking, Internet of Things, and cloud IT/application hosting. Indeed, the top revenue generating services motivating service providers to embrace SDN are cloud-based IT and applications, content and entertainment delivery, machine-to-machine applications, and managed services for business and individual users.

Service provider networks will have to harness SDN and NFV to improve the agility and capacity of their service networks to address these demands, ACG says. They'll use SDN/NFV for automated service provisioning, traffic steering, custom applications/services, application-driven service chains, transport path optimization, SLA monitoring and enforcement, operations simplification and a reduction in capital costs.

"Many operators are operating at pretty high scale," says ACG analyst Paul Parker-Johnson. "One of the things NFV platforms allow them to do is deploy a solution quickly into a tenant context. They can deploy functionality just as another module, just as another resource in the cloud."

Early use cases of data center SDN were in cloud service providers with enterprise data centers still in the lab trial phase, Grossner notes. They have the scale to benefit from the optimizations promised by SDN.

And cloud service providers are under pressure to reduce costs to make a profit from offering cloud services like IaaS, PaaS and NaaS to enterprises.

"The urgency was there because of the requirement to be less expensive overall, and the scale where the potential cost savings was large enough to justify the investment" in SDN and NFV, Grossner says.

Infonetics found that 80% of the service providers responding to a 2012 survey are including the OpenFlow SDN protocol and API in their purchasing considerations. OpenFlow manipulates the forwarding of switches downstream from a centralized SDN controller.

Google is using OpenFlow to interconnect 12 worldwide data centers over 10G links. And Verizon sees OpenFlow as a standard way to implement SDNs across multivendor equipment to centralize network intelligence from a high number of remote locations to its more accessible data centers.

OpenFlow and SDNs would enable Verizon to manage its network elements more flexibly, the carrier has said, so that it can explicitly define paths that might be based on service awareness, or subscriber awareness, or the state of network congestion and other capabilities.

NFV will be used to cut down on the number of hardware elements in these networks. Led by seven major communications service providers, NFV provides a standards-based approach to virtualizing a range of telecom applications, thus enabling them to run on industry standard servers.

The European Telecommunications Standards Institute (ETSI) is defining the NFV standard.

Infonetics last year found that carriers rated content delivery networks (CDN), IP multimedia subsystems, and virtual routers/security gateways as the top applications for NFV.

AT&T is currently reviewing Request For Information (RFI) documents from vendors on their plans to embrace SDN and NFV in their products and product architectures to align with AT&T's Domain 2.0 virtualization strategy. Domain 2.0 is a network virtualization project that looks to embrace commodity, white box hardware and SDN controllers.

Jim Duffy has been covering technology for over 28 years, 23 at Network World. He covers enterprise networking infrastructure, including routers and switches. He also writes The Cisco Connection blog and can be reached on Twitter @Jim_Duffy and at jduffy@nww.com.